through thick and thin

through thick and thin idiom
Despite all obstacles or adversities, as in She promised to stand by him through thick and thin. This term alludes to penetrating a forest with both thick and sparse undergrowth. Today it is nearly always used with the idea of supporting something or someone in all circumstances, as in the example. [Late 1300s]

The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

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